Validate a set of ABR variants.
Shared by buildAbrLadderArgs and abrLadder so both entry points reject the same inputs — otherwise a bad variant only fails on whichever path you happened to take.
buildAbrLadderArgs
abrLadder
Validate a set of ABR variants.
Shared by
buildAbrLadderArgsandabrLadderso both entry points reject the same inputs — otherwise a bad variant only fails on whichever path you happened to take.